| dc.description.abstract | This thesis applies hydrogen as a fuel and combines three clean energy-saving technologies, including heat-recirculating, catalytic reaction and thermoelectric conversion, to devise a clean portable thermoelectric generator (TEG). This TEG system consists of three key parts: (1) A Swiss-roll catalytic heat source (SRCHS), (2) a thermoelectric module (TEM) and (3) a heat sink (HSI), in which the TEM is sandwiched between the SRCHS and the HSI. The SRCHS made of B85 material with properties similar to that of the ceramic material is manufactured by a CNC machine to have a 1.5-turn Swiss-roll channel with a cross-sectional area of 4 mm × 4 mm. The cross-sectional area of SRCHS is 50 mm × 50 mm with a height of 10 mm, in which various lengths (5 ~ 10 mm) of honeycomb platinum catalysts located inside the SRCHS`s channel are need to generate heat from the surface reaction between premixed H2/air mixtures and Pt catalyst. Because of very low heat conductivity of B85 material together with the Swiss-roll heat recirculation, the SRCHS features as a uniform heat source for the TEM provided that a copper plate with very high heat conductivity is used. In addition, we apply a water cooling HSI, so that the wanted temperature range (50 ~ 250℃) across the TEM can be stably controlled. For temperature measurements, ten K-type thermocouples positioned at different locations along the SRCHS flow channel as well as three K-type thermocouple films positioned on the upper copper plate surface are applied to measure temperature distributions of the SRCHS. Various hydrogen concentrations in volume percentage ([H2] = 8 ~ 12%) are used with a wide range of the flow Reynolds number (Re = VfD/?) varying from 500 to 2000, where Vf is the mean velocity of reactants, D = 4 mm is the width of the flow channel, and ? is the kinematic viscosity of H2/air mixtures. This study also measures emissions of [H2], [O2], and [NOx] using the gas analyzer. For numerical simulations, a 3D reacting model is established using CFD-RC packages combined with a 13-steps platinum surface reaction mechanism with the consideration of heat losses to predict chemical reacting flows in the SRCHS. Moreover, efforts are made to simulate heat and electric fields of the Seebeck effect for the TEM by using the effective contact area and the proper Seebeck coefficient of the TEM. Thus, the relation between the open circuit voltage and the temperature gradient can be simulated and obtained. Numerical results are found to be in reasonably good agreement with experimental data. Finally, when using two segments of catalysts each having 5 mm long placed inside the channel of the SRCHS with the water cooling HSI, the TEG system has the highest power density up to 520 mW/cm2, where [H2] = 12%, Re = 1500, and ΔT ～ 200℃ between the cold and hot sides of TEM with a mechanical load of 200 psi. This novel portable TEG system is a pollution-free power generator which is useful for many small electric devices.
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